Cylinder for forming or treatment of material webs

ABSTRACT

A CYLINDER FOR FORMING OR TREATING WEB MATERIALS, THE SHELL OF THE CYLINDER BEING FORMED OF A THIN, ENDLESS BAND WHICH IS AXIALLY STRETCHED BETWEEN TWO RINGS SUPPORTED ROTATABLY IN SUCH A MANNER THAT THE TENSION IN THE BAND IS MAINTAINED.

Feb.23, 1971 MLFSEN 3,564,725

-, CYLINDER FOR FORMING OR TREATMENT OF MATERIAL WEBS Filed March 25, 1969 2 SheetsSheet 1 Feb. 23, 1971 ALFSEN 3,564,725

CYLINDER FOR FORMING OR TREATMENT OF MATERIAL WEBS Filed March 25, 1969 2 Sheets-Sheet 2 FIG.

United States Patent US. Cl. 34121 4 Claims ABSTRACT OF THE DISCLOSURE A cylinder for forming or treating web materials, the shell of the cylinder being formed of a thin, endless band which is axially stretched between two rings sup ported rotatably in such a manner that the tension in the band is maintained.

The present invention relates to a cylinder for forming or treatment of material webs, for instance paper webs. As will be known, present day drying of paper etc. is usually carried out over a so-called Yankee cylinder, the shell of which is cast and provided with bottom ends and with shaft journals mounted in support bearings on the base. Such cylinder shells are frequently of such embodiment and dimension that they weigh from 60 to 100 tons and the mechanical requirements are such that the walls must be thick, which again leads to comparatively great resistance to heat transference. They are most frequently heated by means of steam and the usual problems connected with steam systems and condensation are then incurred. A conventional cast cylinder of this type is also subject to great strain when heated and the period of time necessary to heat the cylinder to working temperature depends to a great extent on the strain produced by thermal tension in the cylinder. -It is thus not possible freely to select the temperature most suitable to the material to be treated.

The main object of the present invention is to overcome the disadvantages connected with a Yankee cylinder, and to provide a cylinder which may be constructed with a very thin cylinder shell and, in regard to the overall construction, is such that expansion and contraction due to temperature variations does not cause strain such as necessitate great mechanical strength and thereby large and heavy constructions.

Thin walled cylinders which are suitable for use as e.g. drying cylinders in paper machines have long been an aim hitherto unattained since it is diflicult according to known technique, to effect a thin cylinder shell that will retain its shape. In accordance with the present invention the said problems are solved by forming the thin cylinder shell from a thin, endless band, which at the edges thereof, is connected to struts which are secured in supporting rings. The struts are subjected to spring tension at least at one edge of the band and pull the cylinder shell taut, at least in axial direction, with the force desired. These forces are absorbed in the mountings of the supporting rings which are prevented from moving toward each other.

The cylinder shell may, in this manner, be constructed of a thin stretched web of sheet material, wire cloth, plastic or other suitable material, and, because of the small amount of material needed, it is possible to use expensive material in the cylinder shell such as stainless steel, and, since great and relatively rapid temperature variations do not lead to damaging strain, the temperature to which the cylinder shell is heated may be selected in relation to the material web to be treated. The sus- 3,564,725 Patented Feb. 23, 1971 pension of the cylinder shell may be carried out in various ways with struts that are resiliently mounted to rotatably mounted support rings. The tension may be provided by one of any number of known stretch means, including e.g. pneumatic or hydraulic means or the so-called disc springs.

In order that the invention may be more readily understood it is further described in the following with reference to the drawing, where:

FIG. 1 in diagram form shows a cylinder embodiment according to the invention viewed at right angles to the axis of rotation and partially in section,

FIG. 2 shows the cylinder viewed from one end and in section,

FIGS. 3 and 4 show details of the stretching of the cylinder shell viewed in plane and vertical section respectively, and

FIGS. 5 and 6 show the blowing on of a heat medium, mainly in vertical section along a plane through the axis of rotation viz along the line VV on FIG. 6 and in vertical section at right angles to the plane through the axis of rotation respectively.

As shown on the drawings, the cylinder has a cylinder shell of thin material, e.g. stainless steel, a few millimeters thick, and at the ends thereof the cylinder shell is connected to strong support rings 3 on both sides by means of resilient struts 2. The support rings are rotatably mounted but unable to move toward each other as this would reduce the stretch force with which the struts 2 act on the shell 1. In the embodiment example shown, the support rings 3 (see FIG. 4) have a V-shape outer peripheral groove 4 which is adapted to the support rollers 5 which in turn are mounted with thrust bearings and are unable to be axially displaced. The support rollers 5, as shown in FIG. 2, are evenly distributed around the circumference of the support rings 3, and the number of struts around the cylinder shell 1 on both sides is adapted to the purpose, and on FIG. 2 a large number of struts 2 is shown. The struts 2, as shown on FIG. 4, may be resiliently mounted in support ring 3 by means of a suitable number of small disc springs 6- and a holder 7 forms an attachment for the edge of the cylinder shell 1. As will be seen on FIG. 3, the edge may be provided with tongues 8 around the entire circumference for attachment in the holders 7 on the struts 2 and a satisfactory connection thereof entails no problems.

The cylinder may be effected in various ways e.g. with cylinder metal surface of sheet for heating of the cylinder surface, it may be made of perforated material for blowing of air and it may for instance be made of wire cloth.

It is to be emphasized that the cylinder according to the invention is not restricted to use as drying cylinder as it may be used for any form of treatment of any type of wet-form material, e.g. conditioning, setting, shrinking, dressing etc., and the cylinder may also be used advantageously for forming of the web material, e.g. by spraying a suspension onto the cylinder to form a material web.

The principle of construction as described herein may be used to advantage for cylinders of dimensions previously considered impossible in practice, it is also lightweight and may be driven at great speed.

The example illustrated serves merely to illustrate the invention and forms no restriction thereof since other embodiments may be envisioned which fall within the scope of the invention, e.g. the mounting of the support rings may be undertaken in other ways than that illustrated and described herein. As an alternative or complement, the support rings may be mounted so as to be axially movable and preferably tensioned. In some cases it 3 may be sufiicient to arrange a spring suspension or the like at one edge of the band only.

The heating of the band 1 may be undertaken directly on the interior of the band by means of natural gas, propane gas, oil burners or the like. However, at the present time at least it is considered most advantageous to heat the band by blowing on the inner side thereof a heating medium such as hot air or furnace gas, the blowing being suitably carried out by means of a blower of fundamentally the same type as that described in the inventors previous patents, e.g. Swedish Pat. No. 195,088. Such a system is shown in diagram in FIGS. 5 and 6.

The open portions between the struts allow cooling of these portions by air flow, such that little transfer from the cylinder shell to the support rings occurs.

It will be seen that the heating medium, e.g. hot air is supplied through a central channel 9, and from this the air branched radially outwards towards the inner side of the band 1 through elongated nozzles which blow the hot air against the inner side of the band 1 through apertures 11 in the bottom 12 of an outlet box 13 which is in communication with an outlet channel 14 concentrically arranged around the inlet channel 9. Since such systems are described in detail in other parts of the accessible literature, it should not be necessary here to describe this further in connection with the present invention. It is merely pointed out that the invention offers good possibilities for variation of the heating, both over the width of the web and in the circumferential direction of the cylinder, e.g. by the division into zones with preferably decreasing drying temperature.

It will be clear to the skilled person that a drying cylinder in accordance with the invention is very light weight when compared to a Yankee cylinder. This permits lower cost both in procurement and in regard to the costs of the base and mounting. The starting-up time is as short as 10-20 minutes moreover, in contrast to the 12-14 hours 4 needed for previous constructions. As the mass is reduced so is the rapidity of adjustment increased which in turn leads to improved quality of the web formed or treated, and also less wastage and improved operating economy.

Modifications and amendments of details can be undertaken within the scope of the inventive idea.

Having described my invention, I claim:

1. A cylinder for forming or treating web materials thereon which comprises a thin rotatable cylindrical shell having two circumferential edges; two rotatable support rings axially aligned with said shell, one support ring outwardly adjacent each of said edges; a plurality of biased struts connecting said edges to said rings; and two sets of a plurality of bearing rollers, one set for engaging each of said support rings; said array of support rings, biased struts and bearing rollers maintaining the cylindrical shell taut under axial tension.

2. The cylinder as defined by claim 1 wherein the biased struts are spring-loaded and the support rings are immobile axially to provide cooperatively said tension.

3. The cylinder as defined by claim .1 wherein the support rings and bearing rollers have convex and concave outer peripheries for radial engagement with one another and the support rings are immobile axially.

4. The cylinder as defined by claim 1 wherein a central channel defines a heat source within the cylindrical shell.

References Cited UNITED STATES PATENTS 3,416,334 12/1968 Candor et al 34-133X MARTIN P. SCHWADRON, Primary Examiner T. W. STREULE, Assistant Examiner U.S. Cl. 34-133 

